Shaft seals are used in various fields of the technology for sealing between stationary bodies and rotatable bodies arranged coaxially thereto, for instance for sealing a rotating shaft with respect to a stationary housing or for sealing a stationary axle with respect to a hub rotating about the axle. The use of shaft seals is intended for example to prevent the exit of lubricant present in the clearance between the two bodies and also to prevent the entry of contaminants into the clearance.
In some fields of application, it can be necessary to produce a coupling between the stationary and the rotatable body, which is suitable for pressure-medium transmission. In vehicles, it is for example desirable to enable the transmission of compressed air from a stationary wheel axle into a wheel hub which is rotatably mounted on the wheel axle in order to thereby enable autonomous tire-pressure regulation to be carried out—even during the journey. In long distance haulage, for instance, the tire pressure can be adapted in this way to changes in load conditions, road surfaces or environmental temperatures.
To realise such a compressed-air transmission in vehicles, it has been proposed that, for sealing between the wheel axle and the wheel hub, two shaft seals, for example commercially available Simmerrings®, should be arranged at an axial spacing from one another in order to form a pressure-tight annular cavity between the shaft seals, through which compressed air can be transferred from a compressed-air line, which is provided on the wheel axle and leads into the cavity, into a compressed-air line which is provided on the wheel hub and leads out of the cavity. Arrangements of this type are disclosed for example in publications DE 10 2009 057 158 A1 and DE 690 05 731 T2. The solutions described therein have, however, proven to be of little use in practice owing to the spatial requirement which is generally too large for today's vehicle axles and owing to the service life being too short under the prevailing pressure load.
It is therefore the object of the invention to provide a solution with which a coupling which is suitable for the pressure-medium transmission can be realised in both space-saving and durable manner between a stationary body and a rotatable body arranged coaxially thereto.